Review:“The Anthropocene Equation” by Gaffney & Steffen

This paper claims to represent the disruption of the climate system by humans in the form of a mathematical equation and then warns that the climate could reach a totally new dangerous equilibrium point very different from any climate that the earth has ever experienced in the past. The authors claim to prove that all non-human effects on the “earth system” add to zero, i.e there are presently no natural fluctuations in climate. It is concluded that human induced changes in the biosphere could be discernible on earth for millions of years. 

To an audience that does not understand mathematics, the equation
     𝑑𝐸 𝑑𝑇 = 𝑓(𝐻) 
(where  H = f(P, C, T) , T = f (En, K, Pe) and A, G and I tend to zero)  may give an impression of sophistication and precision, however it is effectively meaningless and not useful in any way. 

Where maths is used to model natural or manmade systems the variables in the equations must represent some measurable quantity which will have a tangible unit of measurement. Physicists, for example, will measure mass in kilograms, and energy in Joules and the production of energy is given by the equation E = mc2 where c is the speed of light (measured in meters per second). Engineers and economists will use maths in a similar way and variables will always represent real measurable quantities. 

By contrast the single equation in this paper uses undefinable and unmeasurable variables which are combined in a completely unspecified manner to produce an equation that predicts nothing and has no conceivable possibility for validation. All of the variables represent nebulous ideas such as “political economy” “Technosphere” and “Knowledge” , given the symbols Pe , T and K respectively, that may look impressive enough to convince an unwitting journalist that this is real mathematics. Unlike E = mc2, which can be checked by measurement and has survived the test of time, the “anthropogenic equation” cannot be checked because none of the variables are measurable. It thus uses pseudo-mathematics to produce pseudo-science. It is as meaningless as the answer to “life the universe and everything” which according to The Hitch Hikers Guide to the Galaxy is 42. 
 
Prof Peter Ridd
Physics Department
James Cook University